These Barnstable residents say wind substations are a danger to public health. Here's why.

• A Barnstable group petitioned the EPA to review Avangrid's offshore wind projects due to drinking water concerns.
• The petition cites potential threats to the Cape Cod sole source aquifer from substations and underground cables.
• The group argues the EPA has legal grounds to intervene under the Safe Drinking Water Act and other regulations.

Save Greater Dowses Beach, a Barnstable-based group with members across Cape Cod and New England, is appealing to the Environmental Protection Agency to intervene in what it sees as a serious threat to the region’s drinking water from offshore wind development.

The organization recently submitted a petition from 37 Barnstable residents. They are asking the agency to conduct an impartial review of Avangrid Renewables’ offshore wind projects, which would bring electrical cables ashore and connect them to large substations in Barnstable.

"Our objections to these cable landings are many, but the danger posed to human health and safety is at the top of our list. That naturally includes protecting the sole source of drinking water for the people of Barnstable and Cape Cod," said Susanne Conley, SGDB chairwoman and co-founder.

Avangrid declined to comment on the petition.

Petition questions substation sites on sole source aquifer

The petitioners are specifically questioning the substations in Avangrid's New England Wind 1 and New England Wind 2 projects, formerly Park City Wind and Commonwealth Wind. They say the proposed sites sit on land vital to recharging the Cape Cod Sole Source Aquifer, which supplies drinking water to 250,000 year-round residents — and many more in summer — and are near areas set aside to protect future water sources.

They also express concern about the already completed substation in the industrial park off Industrial Drive in Hyannis, which supports the Vineyard Wind project.

"We’re asking EPA to consider the cumulative environmental hazard of three extra high voltage substations built over the aquifer," Conley said, adding the group believes the Vineyard Wind substation "should never have been built in such close proximity to an apartment complex."

A plea for 'legally required' federal review

The group argues that the EPA is legally required to review the plans under the Safe Drinking Water Act of 1974, which calls for federal oversight of any project using federal funds that could affect a sole source aquifer.

Even though the wind projects aren't directly funded by the government, the group asserts that they depend on significant federal tax credits under the Inflation Reduction Act to cover about a third of their costs, which top $5 billion. The petition argues that an earlier EPA decision not to intervene was based on an overly limited view of what counts as federal funding and asks the agency to take another look under the current leadership.

The petition also highlights the agency's responsibilities under the Clean Air Act of 1970, as well as its own Sole Source Aquifer program.

“The EPA cannot simply ignore its responsibility under the Sole Source Aquifer Program,” the petition states, pointing out that "the health and well-being of the residents of Barnstable and the surrounding region of Cape Cod are at stake."

The petitioners cite "significant hazard to public health," asserting the projects "all require individual substations that utilize toxic dielectric fluid and potential use of sulfur hexafluoride, of SF6, a toxic greenhouse gas that lingers in the environment.

The developer has said that state-of-the-art containment systems — described publicly as a “bathtub” — would prevent any leaks from getting into the soil or water table. But the petition cites expert testimony warning that fires, explosions, and even truck accidents during transport to and from the substations could cause serious spills that could permanently contaminate the aquifer.

Concerns about heat, toxins, and water quality

The group also worries about the heat that underground high-voltage cables would generate. Engineers say the cables can radiate temperatures up to 180°F, and although they’ll be buried in concrete, they’ll lie at the same depth as Barnstable’s drinking water pipes.

"This has caused serious concerns for the COMM Water Commission, which is currently incommunication with the proponent to determine the extent of thermal effect on the drinkingwater of three of the town’s seven villages," such as bacterial growth, according to the petition.

The water commission and the developer are currently negotiating the terms for an independent study to determine how the duct banks may affect water quality, according to the petition.

"This level of uncertainty should be of concern" to the EPA, the petition states, especially "given the proponent’s stated desire to begin duct bank construction in the fall of 2025."

The group further asserts that the overall permitting process for the projects has not treated the town fairly. The state Energy Facilities Siting Board denied the town’s request for “intervenor” status, which would have allowed the town to participate formally in decisions about where the substations would be built.

EPA asked to reconsider scope and precedent

Finally, the petition questions why the EPA did not extend its onshore permitting beyond air quality concerns for offshore operations.

SGDB argues that the EPA stepped in before because of concerns about aquifer contamination — like when a controversial firing range was proposed at Joint Base Cape Cod — and should do so again.

"We ask for the same consideration for the same reason," the petition states, namely, potential contamination of the same sole source aquifer.